Thermal behavior and water adsorption of natural and modified sepiolite having dolomite from Turkey

Abstract

The water adsorption properties of sepiolite having dolomite supplied from Eskisehir region and their exchanged forms (K+, Na+, Mg2+ and Ca2+) were investigated. The sepiolite samples were characterized using XRD, TG-DTA, DSC and nitrogen adsorption methods. The temperature ranges were determined for the dehydrations of hydroscopic and zeolitic water as 30-200A degrees C, for the dehydration of the bound water as 250-750A degrees C and for the dehydroxylation of hydroxyls as 810-850A degrees C in the sample. It was observed that the value of percent mass loss for natural and modified samples varied in the range from 36.70 to 39.05%. Two mass loss steps for all samples were observed using a differential scanning calorimetry (DSC) in the range of 30-550A degrees C. Adsorption isotherms for water on natural and modified forms were obtained at pressures up to 2.39 kPa. Uptake of water increased as K-SEP.< Na-SEP.< Mg-SEP.< Ca-SEP. for sepiolite samples at 293 K.